From the past, silicone particles are often used in cosmetic compositions for the purposes of imparting a pleasant feel on use (e.g., smooth or silky feel) and spreadability thereto. In particular, fine particles comprising spherical fine particles of silicone elastomer coated with polyorganosilsesquioxane as disclosed in JP-A H07-196815 are used in many cosmetic compositions because of soft feel, non-cohesion, and good dispersion.
The silicone particles do not possess a UV screen effect. When these particles are compounded in cosmetic compositions intended for UV screening, the particles in a cosmetic coating permit UV radiation to be transmitted thereby, detracting from the UV screening effect of the cosmetic compositions. The problem worsens particularly when silicone particles have a large particle size.
On the other hand, silicone particles which are surface coated with inorganic particles are known. For example, JP-A S63-27410 discloses spherical particles in which surfaces of thermosetting silicone resin particles are coated with titanium oxide, iron oxide or other pigments in nano-particulate form. JP-A S63-68513 discloses spherical particles in which surfaces of thermosetting silicone resin particles are coated with metal compounds, metals or other pigments in nano-particulate form. JP-A H04-348143 discloses particles in which surfaces of silicone rubber particles are coated with metal oxide in nano-particulate form. JP-A H06-001709 discloses particles in which surfaces of silicone resin particles are coated with inorganic particles. WO 2004-055099 discloses a powder in which cured silicone particles are covered with surfactant-bearing inorganic fine particles. JP-A 2006-188592 describes that silicone rubber particles are surface coated with inorganic fine particles and treated with an organosilicon compound having a silicon-bonded hydrolyzable group. Among the foregoing silicone particles, those particles having a UV screening effect are expected not to adversely affect the UV screening effect of a cosmetic composition into which they are compounded. Those particles having an antibacterial effect are expected to impart a deodorant effect to an antiperspirant cosmetic composition into which they are compounded. These silicone particles, however, are not effective for imparting a pleasant feel on use and spreadability because the particle surface is not formed of silicone.
JP-A 2006-188592 describes treatment of particles with an organosilicon compound having a silicon-bonded hydrolyzable group, which is least effective for imparting a pleasant feel on use and spreadability.
To meet the demand for particles capable of imparting a pleasant feel on use and spreadability despite the presence of inorganic particles, silicone particles containing inorganic particles therein were proposed. For example, JP-A H05-32914 discloses inorganic filler particles which are surface coated with a hydrosilylation reaction product of an organohydrogenpolysiloxane having an ethylenically unsaturated group. JP-A H05-221640 discloses titanium oxide particles which are surface coated with a hydrolytic condensate of a trialkoxysilane. JP-A H10-324817 discloses titanium oxide particles having a hydrolytic condensate of an organosilane compound applied to surfaces thereof. JP-A 2001-354776 discloses spherical particles of silicone elastomer containing titanium oxide fine particles. JP-A 2004-203780 discloses spherical particles of polyorganosilsesquioxane containing UV screening inorganic fine particles. Because of the particle surface formed of silicone and containment of inorganic particles, these particles can impart a pleasant feel on use and spreadability as well as inorganic particles' properties. However, since inorganic particles are contained within silicone particles, more inorganic particles are necessary in order to provide satisfactory properties such as a UV screening effect, giving rise to a coloring problem. In the case of silicone particles containing titanium oxide fine particles, for example, substantial loading thereof in a cosmetic composition should be avoided because the cosmetic composition otherwise becomes too white.